Optical solar reflector smart radiators are able to control the temperature of spacecraft. This work demonstrates a novel smart optical solar reflector using a patterned thermo-chromic VO2 plasmonic meta-surface design. The VO2 meta-surface combines the temperature induced phase transition of VO2 with plasmonic resonances resulting in a significant enhancement of the infrared absorption. The enhanced absorption obtained at a reduced VO2 coverage results in superior emittance tunability Δε and lower solar absorptance α compared to a corresponding thin-film reflector. An emittance tunability of 0.48 is obtained for the meta-reflector design, representing a 30% improvement compared to the unstructured film. Meta-surface based smart optical solar reflectors offer a new route toward energyefficient and cost-effective passive thermal control systems of spacecraft and other surfaces.

Optical Solar Reflectors are devices that combine high reflection for visible wavelengths with a strong emissivity in the infrared. Compared to the conventional rigid quartz tiles used on spacecraft since the 1960s, thin-film solutions can offer a significant advantage in weight, assembly and launch costs. Here, we present a metasurface based approach using an Al-doped * To whom correspondence should be addressed † Electronics ‡ Physics ¶ CREO § NILT ZnO (AZO) transparent conducting oxide as infrared plasmonic material. The AZO is patterned into a metasurface to achieve broad plasmonic resonances with enhanced absorption of electromagnetic radiation in the thermal infrared. In the visible range, the transparent conducting oxide provides low losses for solar radiation, while intrinsic absorption losses in the ultraviolet range are effectively suppressed using a multilayer reflecting coating. The addition of high-emissivity layers to the stack eventually results in comparable emissivity values to the thin plasmonic device, thus defining a window of opportunity for plasmonic absorption as a design strategy for ultrathin devices. The optimized experimental structure achieves solar absorptance (α) of 0.16 and thermal emissivity (ε) of 0.79. Our first prototype demonstrator paves the way for further improvement and large-area fabrication of metasurface solar reflectors, and ultimately their application in space missions.

Plasmonic metasurface coloration has attracted considerable attention in recent years due to its industrial potential. So far, demonstrations have been limited to small patterned areas fabricated using expensive techniques with limited scalability. This study elevates the technology beyond the common size and volume limitations of nanofabrication and demonstrates aluminum‐coated polymer‐based colored metasurfaces of square‐centimeter size by embossing, injection molding, roll‐to‐roll printing, and film insert molding. Different techniques are compared and the requirements and bottlenecks in terms of master fabrication, replication, metallization, and protection coating for large‐scale production of sub‐wavelength metasurfaces are discussed. Most notably, it is demonstrated that plasmonic metasurface colors are compatible with film insert molding. The results indicate a promising future for plasmonic colors as a viable alternative for decorating mass‐produced polymer parts.

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Ultra-low power electrically reconfigurable magnetoelectric microwave devices J. Appl. Phys. 112, 073915 (2012) Broadband and ultrathin screen with magnetic substrate for microwave reflectivity reduction Appl. Phys. Lett. 101, 154101 (2012) Tunable, narrow-band, all-metallic microwave absorber Appl. Phys. Lett. 101, 141115 (2012) Insertable system for fast turnaround time microwave experiments in a dilution refrigerator Rev. Sci. Instrum. 83, 093904 (2012) Coherent terahertz radiation from high-harmonic component of modulated free-electron beam in a tapered twoasymmetric grating structure Appl. Phys. Lett. 101, 123503 (2012) Additional information on J. Appl. Phys. We analyze ultra strong non-resonant field enhancement of THz field in periodic arrays of nanoslits cut in ultrathin metal films. The main feature of our approach is that the slit size and metal film thickness are several orders of magnitude smaller than the wavelength k of the impinging radiation. Two regimes of operation are found. First, when the grating period P ( k, frequency-independent enhancement is observed, accompanied by a very high transmission approaching unity. With high accuracy, this enhancement equals the ratio of P to the slit width w. Second, when the grating period approaches the THz wavelength but before entering the Raleigh-Wood anomaly, the field enhancement in nanoslit stays close to that in a single isolated slit, i.e., the well-known inversefrequency dependence. Both regimes are non-resonant and thus extremely broadband for P < k. The results are obtained by the microscopic Drude-Lorentz model taking into account retardation processes in the metal film and validated by the finite difference frequency domain method. We expect sensor and modulation applications of the predicted giant broadband field enhancement.